Recovery of sulphur



June 21, 1932. R, BACON ET M 1,864,290

RECOVERY OF SULPHUR Filed Feb. 26, 1930 e504 (one e/Jzra/a r INVENTORS IRAYMQND FT BACON H SNFey T. Horch KiSS'Jr BY PMM; www5 m ATTORNEYS Patented June Z1, 1932 STTES RAYMOND F. BACON, 0E' BRSTXVILLE, AND HENRY T. HOTCHKISS, JR., OF NEW ROGBELLE, NEEV YORK; SAID HOTCHKSS, JR., ASSIGNOR TO SAE) BACON RECOVERY or sULrHUR Application filed. February 26, 1930. Serial No. 431,468.

This invention relates to the recovery of sulphur and has for an objectthe provision of an improved process vfor recovering sulphur from heavy metal sulphide ores. 'More particularly, the invention contemplates the pro' vision of an improved process for recovering sulphur from materials containing one or more sulphides of iron. The invention further contemplates the provision of an improved process for treating heavy metal sulphide ores such, for example, as ore containing sulphides of iron, copper and nickel.V

volves the treatment Vof ore or 'other metallurgical raw materials or products containing pyrites or other sulphides of iron, alone or in combination With sulphides of other heavy metals such, for example, as copper f and nichel with sulphur chloride and chlorine for the purpose of obtaining free sulphur and/or separating iron from the mass of materi al undergoing treatment.

ln carrying out a process inV accordance with the presentV invention,.a `quantity of ore or other material to be treated is subjected to the action of sulphur chloride and chloiinev under such conditions that ferrous chloride and free sulphur are produced. The operation is so conducted that the sulphur produced is vaporized, leaving a residue containing the ferrous chloride together With chlorides of other heavy metals, such as copper and nickel, when the sulphides of such metals are presf ent in the Vmaterial undergoing treatment.

"H" in) rlhe sulphur produced is condensed and collected as tree sulphur. .The residue containing ferrous chloride is subjected to the action of chlorine to form and vaporize ferrie chloride. The ferrie chloride produced is subjectedto the action of superheated steam' lo produce hydrogen chloride Which is subjected to the action of oxygen to produce free chlorine. The chlorine thus produced is returned to the process The invention will be better understood frein consideration oi the accompanying loivsheet and the following description of #he application ot the invention to the treatnent of ore containing sulphides of iron, copper and nickel.

The ore to be treated is subjected to the action of sulphur chloride and chlorine under the sulphur may be maintained and substanlllhe process ot the present invention in-V is usedtor treating additional ore. The

chlorine when first recovered is mixed With inert gases, and the mixture may be used for regenerating-sulphur chloride and for treating additional ore. The inert gases mixedV With the portion of the chlorine used for regenerating sulphur chloride may be readily eliminated by condensing the sulphur chloride. f Y

When the inert'gases mixed With the chlorineand/or sulphur chloride 'are introduced into the reaction chamber, the reaction chamber may be maintained at a temperature above or below the boiling'point of sulphur; At either or both temperatures, the reaction may be so controlled that? the inert'gases aid in Ysweeping the sulphur from the reactio1 1"chainV duced into the reaction chamber at the end opposite to that at which the ore is introduced and the ore and sulphur chloride and chlorine pass through the reaction chamber in counter-current relationship. The sulphur chloride may be introduced into the reaction chamber in either' the liquid state or the gaseous state. Liquid sulphur chloride will be vaporized immediately after its introduction. The ore is preferably ground to provide particles sufficiently small to pass a 100-mesh screen in order that intimate contact of the sulphur chloride and chlorine with the sulphide particles may be obtained.

The process is preferably so controlled that a temperature of about L50" C. is maintained near the ore charging end of the reaction chamber, and a temperature of about 300 C. to 350 C. is maintained near the discharge end of the reaction chamber. The sulphur chloride and chlorine in any desired concen- `trations and at any desired temperatures are introduced into a portion of the reaction chamber which is maintained at a temperature of about 300o C. to 350 C. -The sulphurY chloride and chlorine and the metal sulphides react to produce elemental sulphur, ferrous chloride and the chlorides of copper and nickel. The admissionof-ore and sulphur chloride and chlorine is preferably so regulated that all of the sulphur liberated is vaporized as elemental sulphur, all of the sulphur chloride and chlorine admitted is consumed, and substantially all of the iron sulphide is converted to ferrous chloride.

Any ferric chloride vwhich is produced in,-

tlie reaction chamber will be vaporized and swept along with the inconiingsulphur chlo-v ride and chlorine to meet theentering iron sulphide-bearing material.

i ride will reactwith the sulphides toforin ferrous chloride and sulphur chloride. Sulphurchloride which is formed will also react with theheavy metal sulphides.V The reactionbetween the sulphides and the sulphur chloride and chlorine isexotherinic and the desired temperatures may be maintained by the heat developed.

chamber at a temperature of about 300 C.

to V350 C. The vaporized sulphur is collected and condensed.

` The liot residue containing ferrous chloride is subjected to the action ofchlorine gas to produce and vaporize ferric chloride. The

treatment of the ferrous chloride-bearing inaterial is preferably conducted in a rotary reaction chamber which is so'constructed and arranged that ferrous chloride-bearing material 'charged into one end portion will move progressively toward the other end portion Y ship.

The ferric chlo-.V

during its rotation. The ferrous chloridebearing material and the chlorine gas are preferably introduced into opposite ends of the reaction chamber and pass through the reaction chamber in counter-current relation- The ferrous chloride-bearing material thus passes gradually into regions of increasing chlorine concentrations and a substantially complete removal of iron from the mass is assured.

The hot residue contains nickel chloride and copper chloride in addition to ferrous chloride and gangue, and it enters the reac-V tionchamber at ateniperature of about 300 C. The chlorine employed for treating the ferrous chloride-bearing material comprises, in part at least, chlorine which is recovered in a subsequent step of the process from ferric chloride produced during the course of the treatment, and it is contaminated with inert gaseswhich are introduced into t-he system. The inert gases may be utilized for sweeping the ferric chloride from the reaction chamber, and the reaction chamber may, therefore, be maintained at atemperature belowy the boiling point offerric chloride. Satisfactory results may be obtained if the reaction chamber is maintained at a temperature of about 300 C., but temperatures above 300 C. and preferably above 315 C., the boiling point of ferric chloride, are more desirable, a temperature of about 350 C. being very satisfactory.

vA reaction between ferrous chloride and chlorine proceeds according to the following equation:

The chlorides of nickel and copper remain unchanged and do not Vaporizeto any substantial extent' when a temperature between about 3000. and' 350 C. is maintained.

A residue containing'the chlorides of copper and nickel and the gangue contained in the original ore is discharged from the rechamber. The ferric chloride is hydrolyzed and ferric oxide and hydrogen chloride are formed, the reaction proceeding according to the following equation:

i In carrying out the hydrolysis of ferricl chloride, ferric lchloride vapor and superheated steam are introduced together into the reaction chamber in such a manner that intimate mixing will result. The reaction may be conducted conveniently at a temperature of about 300 C. to 400 C. Good results may be obtained if the reaction chamber is maintained at a temperature of about 350 C.

The ferrie oxide will be produced in the form of a line powder which may be permitted to settle out in the reaction chamber. The gases issuing from the chamber contain hydrogen chloride and water vapor and they are passed through a suitable drying apparatus such, for example, as a packed tower having sulphuric acid trickling therethrough to separate the water vapor and produce dry hydrogen chloride.

The gases containing the dry hydrogen chloride are introduced into a catalytic reaction chamber with one to seven times their volume of air, depending on the concentration of the hydrogen chloride available. The air is preheated to a temperature above 420 C. and preferably to a temperature between 520 C. and 530 C. If desired, the hydrogen chloride may also be preheated.

The catalytic reaction chamber preferably consists of a tower, or a series of communicating towers packed with porous material having a very large surface per unit of volume such, for example, as pumice, brick, cinders and the like. The packing material should be of such a nature that it will be inert to the reagents and the products of the reaction. The packing material is covered or impregnated with the catalyst which promotes a reaction between hydrogen chloride and oxygen, and which may consist of one or more chlorides or sulphates of metals such, for example, as copper and nickel. The salts may be applied as such directly to the packing material or they may be formed in place as, for example, by the action of hydrogen chloride on copper oxide which is distributed throughout the mass. Means are provided for renewing the catalytic mass as its elliciency becomes reduced. For this purpose two towers, or two series of communicating towers, which may be used alternately are preferably provided.

The apparatus is so constructed that the mass of vcatalyst-bearing material may be maintained at a temperature of from 370 to 400O C. The reaction between the hydrogen chloride and the oxygen of the air is exothermic and it may be so controlled Vas to permit the proper temperature to be maintained.

The reaction will proceed at a temperature as low as 205o C. and a temperature as high as 47 0O C. may be used advantageously. The temperature at which the reaction is conducted will be governed largely by the nature of the catalyst. The temperature employed should be sufficiently low that excessive volatilization of the catalyst is avoided. The reaction involved in this operation does not proceed to completion. The gases issuing from the reaction chamber will consist of a mixture of hydrogen chloride, water vapor and chlorine.

ln view of the fact that the reaction does not readily proceed tov completion, it may be desirable to retreat the issuing gases by subjecting them to a drying operation to remove the water vapor and subsequently passing them through a second reaction chamber. This vprocedure may be repeated two or three or more times if desired. ln carrying out the reaction between hydrogen chloride and the oxygen of air it is advisable to carefully control the proportions of air and hydrogen chloride utilized in order to avoid excessive dilution of the resulting chlorinegas and in order to avoid the incorporation of excessive amounts of free oxygen in the resulting chlorine gas.

The gases are washed with water tos'eparate the chlorine and hydrogen chloride, The separated chlorine is dried with sulphuric acid, and a portion of the dried gas is utilized for treating the residue containing ferrous chloride.

Another portion of the dry chlorine is passed through a molten bath of sulphur which has been obtained by condensing a portion of the sulphur vapor recovered during' the treatment of sulphide-bearing'material with sulphur chloride and chlorine. The sulphur bath is maintained at a temperature above the boiling point of sulphur chloride and the sulphur chloride distills oli as formed. ylhe sulphur chloride vapor may be collected and condensed to eliminate'inert gases, or the resulting mixture of sulphur chloride and inert gases may be conducted directly tc the reaction chamber for-thetreatment of additional ore. lf the sulphur chloride vapor is condensed the liquidV sulphur chloride may be vaporized and returned to the process.

The reaction-between sulphur and chlorine will proceed at temperatures below the boiling point of sulphur chloride, but it is advantageous to conduct the reaction a teniperature above the boiling point of sulphur chloride in order to effect the immediatel removal of the sulphur chloride from the reaction Zone. Condensation of the sulphur chloride vapors permits the removal of inert n gases which enter the system during the admission of air. lf desired, therinert gases may be conducted through a tower containlng solid sulphur in order to scrub out any sulphur chloride vapors contained' therein.`

VThe sulphuric acid used for drying the hydrogen chloride and chlorine is combined with the water used for separating the hydrogen chloride and chlorine and the resulting liquid is heated to recover hydrogen chloride which is returnedto the process.

The sulphuric acid which has been freed from hydrogen chloride is concentrated and again used for drying purposes.` A portion of the steam produced in concentrating the sulphuric acid is utilized for treating the ferric chloride. The first fractions obtained during the concentration of the sulphuric acid will conta-in hydrogen chloride and the use of these fractions in providing super-heated steam for treating the ferric chloride Will permit an added recovery of chlorine.

As a result of the treatment of the hydrogen chloride With air, considerable quantities of inert gases, such as nitrogen, are introduced into the system and must be eliminated to avoid excessive dilution. The inert gases will be mixed with the chlorine gas Which is recovered, and consequently, they Will be returned to the system during the treatment of original ore and during the treatment of the ferrous chloride-bearing residue. Elimination of these gases is effected by condensing the ferrie chloride and by condensing the vaporized sulphur.

The process may be conducted continuously. A source of fresh chlorine is provided to compensate for chlorine losses due to leakage and the production of nickel and copper chlorides. rlhe fresh chlorine may be supplied as chlorine gas, sulphur chloride or hydrogen chloride and the choice Will be determined by the relative costs.

The principal reactions involved in the process are exothermic and enough heat is provided that no heat need be supplied from outside sources. Heat generated during the course of the process may be utilized for carrying out the concentration of the sulphuric acid, vaporization of ferric chloride and other operations in which temperatures must be increased.

wWe claim:

l. The method of treating material containing iron 'sulphide Which comprises subjecting the material to the action of chlorine and sulphur chloride under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, subjecting the ferrous chloride to the action of chlorine to form ferrie chloride, subjecting the ferrie chloride to the action of Water vapor to produce hydrogen chloride, treating the hydrogen chloride to recover chlorine.y and returning the chlorine thus recovered to the process. r

Q. The method of treating material containing iron sulphide Which comprises subj ecting the material to the action of chlorine and sulphur chloride under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, subjecting the ferrous chloride to the action of chlorine to form ferrie chloride, subjecting the ferrie chloride to the action of Water `vapor to produce hydrogen chloride, subjectin the hydrogen chloride to the action of air in the presence of a catalyst to recover chlorine, and returning the chlorine thus recovered to the process.

3. The method of treating ironvsulphidebearing material which comprises subjecting the material to the action of chlorine and' sulphur chloride under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporizeol, collecting the vaporized sulphur, subjecting the ferrous chloride to the action of chlorine to form ferrie chloride, treating the ferric chloride to recover chlorine, utilizing a portion of the recovered chlorine to treat the ferrous chloride, combining another portion of the chlorine with a portion of the sulphur produced to regenerate sulphur chloride, and utilizing the remainder of the recovered chlorine together With the regenerated sulphur chloide to treat additional iron-sulphide-bearing material.

4L. IThe method of treating iron sulphidebearing material which comprises subjecting the material to the action of chlorine and sulphur chloride under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, collecting the vaporized sulphur, subjecting the ferrous chloride to the action of chlorine to form'ferric: chloride, subjecting the ferric chloride to the action of Water vapor to form hydrogen chloride, treating the hydrogen chloride to recover chlorine, utilizing a portion of the recovered chlorine to treat the ferrous chloride, combining another portion of the chlorine with a portion of the sulphur produced to regenerate sulphur chloride, and utilizing the remainder of the recovered chlorine together with the regenerated sulphur chloride to treat additional iron sulphidebearing material.

5. The method of treating iron sulphidebearing material which comprises subjecting the material to the action of chlorine and sulphur chloride under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, collecting the vaporized sulphur, subjecting` the ferrous chloride to the action of chlorine to form ferrie chloride, subjecting the ferric chloride to the action of Water vapor to form hydrogen chloride, subjecting the hydrogen chloride to the action of air in the presence of a catalyst to recover` chlorine, utilizing a portion of the recovered chlorine to treat the ferrous chloride, combining another portion of the chlorine With a portion of the sulphur produced to regenerate sulphur chloride, and utilizing the remainder of the recovered chlorine together With the regenerated sulphur chloride to treat additional iron sulphidebearing material.

In testimony whereof We aiiix our signatures.

RAYMOND F. BACON. HENRY T. HOTCHKISS, JR. 

